High throughput multi-wafer epitaxial reactor

ABSTRACT

An epitaxial reactor enabling simultaneous deposition of thin films on a multiplicity of wafers is disclosed. During deposition, a number of wafers are contained within a wafer sleeve comprising a number of wafer carrier plates spaced closely apart to minimize the process volume. Process gases flow preferentially into the interior volume of the wafer sleeve, which is heated by one or more lamp modules. Purge gases flow outside the wafer sleeve within a reactor chamber to minimize wall deposition. In addition, sequencing of the illumination of the individual lamps in the lamp module may further improve the linearity of variation in deposition rates within the wafer sleeve. To improve uniformity, the direction of process gas flow may be varied in a cross-flow configuration. Combining lamp sequencing with cross-flow processing in a multiple reactor system enables high throughput deposition with good film uniformities and efficient use of process gases.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to the field of chemical vapordeposition (CVD) reactors for thin film deposition, especially ofepitaxial films, and more particularly to CVD reactors employing one ormore lamp-heated reactors and a travelling wafer sleeve exposed to thelamps, absorbing the lamp radiation, and mounting multiple wafers anddefining process gas flow within the wafer sleeve.

2. Description of the Related Art

Epitaxial reactors for use in depositing thin films on wafers bychemical vapor deposition (CVD) may be categorized in terms of theirmethod of heating the wafers, their overall arrangement of the waferswithin the reaction chamber or chambers, and the overall toolarchitecture, including the number of reaction chambers and whetheradditional chambers for preheat and cool down are configured at theentrance and exit of the system, respectively. FIGS. 1-3 illustratethree different types of prior art epitaxial reactors, categorizing eachin terms of these various design aspects.

A prior art pancake-type epitaxial reactor 100 is illustrated in theschematic side cross-sectional view of FIG. 1. The wafers 110 on whichepitaxial films are to be deposited are supported by a susceptor 111.Typical susceptors may be composed of graphite with a silicon carbidecoating. The susceptor 111 is mounted within a reactor chamber 101 intowhich one or more process gases 102 enter through an inlet line 103 to agas passageway included within a stem which also provides mechanicalsupport for rotary motion 140 of the susceptor 111. Electrical eddycurrents flowing within the resistive graphite material of the susceptor111 heat the susceptor 111 and, by conduction, the wafers 110 supportedthereon. These eddy currents are induced by a set of RF induction coils112 mounted beneath the susceptors 111. Process gases 105 enter thereactor chamber 101 through an outlet 104 from the gas passageway in thestem and then flow across the surface of the heated wafers 110. Exhaustgases 115, comprising both product gases from the epitaxial reaction aswell as unused reactant gases, are pumped out of the reactor chamber 101through outlet openings 114.

Pancake-type epitaxial reactors 100 have the ability to deposit thickfilms and dual layers with non-uniformities in the range of 4% inthickness and 7% in resistivity with sharp transitions and low metalscontamination. The rotary motion 140 of the susceptor 111 enhancesdeposition uniformity. Key disadvantages of this type of epitaxialreactor are low throughput, high gas consumption, wafer warpage, andworse uniformities than other types of prior art epitaxial reactors (seeFIGS. 2 and 3). Another important disadvantage is the need for frequentcleaning of the inner surfaces of the reactor chamber 101 due tounwanted deposition of films on these surfaces. This unwanted depositionincreases the cost of ownership due to higher process gas consumptionand increased system downtime for maintenance and cleaning.

A prior art barrel type epitaxial reactor 200 is shown in the schematicside cross-sectional view of FIG. 2. In this type of reactor, wafers 210on which epitaxial films are to be grown are mounted on a multi-sidedgraphite carrier 211, which is held within a reactor chamber 201 on asupport 215 enabling rotary motion 240 to enhance uniformity during thedeposition process. The graphite carrier 211 is heated by an array oflamps 202 contained within one or more reflector assemblies 203 whichare mounted around, and outside of, the reactor chamber 201. Processgases 217 enter the reactor through inlet lines 216 and flow around theoutside of the graphite carrier 211 as illustrated by arrows 220.Exhaust gases 205, comprising both product gases from the epitaxialreaction as well as unused reactant gases, are pumped out through anexhaust line 204. Some of the reactant gases 221 recirculate within thereactor chamber 201, increasing the usage efficiency of the reactantgases during the epitaxial deposition process.

Barrel-type epitaxial reactors have the advantages of good surfacequality and slip performance, with typical thickness non-uniformitiesaround 3% and resistivity non-uniformities around 4%. Throughputs can behigher than for the pancake type reactor. Some disadvantages are aninability to deposit dual layers and relatively high film resistivities.This type of reactor is currently the main type used in CMOSsemiconductor manufacturing.

A third type of prior art epitaxial reactor is illustrated in FIG. 3, aSingle/Mini-Batch™ lamp heated reactor 300. In this reactor 300, asingle wafer 310 is processed within a reactor chamber comprising alower metal portion 301 and a quartz dome 302, which are held togetherby a multiplicity of clamps 303. Typically, the pressures within thereactor chamber may be lower than for other types of epitaxial reactors.A wafer 310 being processed is supported by a carrier 311 which ismounted on a stem 315 extending into the reactor chamber. The stem 315enables rotary motion 340 of the carrier 311 during the depositionprocess to enhance uniformity. Process gases 307 enter the reactorthrough an inlet line 350. The process gases 308 enter the reactorchamber near the level of the wafer 310. The wafer 310 is heated bylight radiation from an array of lamps 330 mounted within a reflectorassembly 331. Exhaust gases 306, comprising both product gases from theepitaxial reaction as well as unused reactant gases, are pumped out ofthe reactor chamber through an outlet opening 305.

The Single/Mini-Batch™ type of epitaxial reactor has a number ofimportant advantages, including the ability to process wafers 310 withno need for a backside seal. Epitaxial films may be deposited with sharpdopant transitions, with low metals contamination, and with lowthickness (1.5%) and resistivity (2%) non-uniformities. In addition,wafers up to 300 mm in diameter may be accommodated in the single waferreactor chamber. Films with good surface quality and no slip may bedeposited with throughputs as high as 8 to 24 wafers per hour. However,an important disadvantage of this type of reactor is the high film costsfor thicker films where the throughputs drop due to the longer epitaxialdeposition times required.

Epitaxial deposition is a process which was pioneered for use in thesemiconductor industry for the manufacture of integrated circuits anddiscrete devices. Typically, a silicon-precursor gas such as silane isinjected close to a hot crystalline silicon substrate to chemicallyvapor deposit a layer of silicon on the substrate, which is epitaxialwith the silicon of the substrate. For these applications, in general,the final value of a fully processed wafer can be fairly high, in somecases, such as for microprocessors, in the tens of thousands of dollarsper wafer. Thus, the economics of semiconductor manufacturing maysupport relatively higher costs for each processing step than would bethe case for other types of semiconductor products such as photovoltaic(PV) solar cell wafers. For these other applications, the cost perprocess step must be relatively low since the final cost of a PV solarcell (typically about 150 mm square) may be in the range of ten dollars,orders of magnitude lower than for most fully processed semiconductordevice wafers (typically 200 or 300 mm in diameter). On the other hand,some film characteristics for PV solar cell applications may be lessstringent than for device wafers, in particular, the required filmthickness and resistivity uniformities.

Epitaxial deposition of a thin-film solar cell has the disadvantage thatepitaxial deposition is typically a relatively slow process in achievinggood epitaxy but the semiconducting light absorbing layers in a solarcell need to be relatively thick. As a result, the deposition times forepitaxial solar cells are typically much longer than for the very thinepitaxial layers typical of modern electronic integrated circuits.

SUMMARY OF THE INVENTION

The present invention provides an improved design for an epitaxialreactor with higher throughput, a wafer sleeve containing a multiplicityof wafers within a small reaction volume to improve usage of processgases and minimize unwanted deposition on the reaction chamber walls,and increased lamp lifetimes through improved lamp temperature control.A high degree of control over film thickness and resistivityuniformities within and between wafers may be achieved in the presentinvention without the need for rotary or other types of wafer motionduring the deposition process, thereby simplifying the design of thereactor chamber. The epitaxial reactor of the present invention maycomprise one or more lamp modules which irradiate a wafer sleevecontained within a reactor frame which also supports the lamp modules.Alternative embodiments of the present invention may employ eitherresistive heating or inductive heating of the wafer sleeve, instead ofradiant lamp heating.

In one aspect of the invention, each lamp module comprises amultiplicity of lamps, typically tungsten-halogen, which radiantly heatthe wafer sleeve through an illumination window, typically quartz. Onthe far side of each lamp, away from the wafer sleeve, is a reflectorassembly, typically gold-coated for maximum IR reflectivity andresistance to oxidation. The lamp module structure may be water cooledwhile each lamp within the lamp module may be air cooled by an array ofopenings behind each lamp which are connected to air plenums. This lampcooling arrangement ensures proper hermetic sealing of the lamp at eachend to preserve the pressure of the cooling air, as well as increasingthe lamp lifetime through proper lamp temperature management. In oneembodiment of the present invention described herein, two lamp modulesare mounted on the reactor frame, wherein each lamp module irradiatesthe wafer sleeve supported within the reactor frame. In an alternativeembodiment, a single lamp module is mounted on one side of the reactorframe, heating the wafer sleeve.

In another aspect of the invention, the wafer sleeve is an assemblycomprising at least two carrier plates, onto each of which a number ofwafers are mounted in good thermal contact with the flat inner surfacesof the carrier plates. The carrier plates are supported and held in afixed close spacing by a pair of end caps. The outer surfaces of thecarrier plates are heated by light from the lamp modules, which radiatethrough windows, preferably quartz. A preferred material for the carrierplates is silicon carbide due to the high absorptivity of siliconcarbide for visible and infrared light.

The process gases for epitaxial deposition may be fed directly into theinterior space of the wafer sleeve by a set of process gas inlet tubeson the top and bottom of the reactor frame. Also on the top of thereactor frame is a set of purge gas inlet tubes, typically supplyinghydrogen gas into the volume within the reactor frame, but outside ofthe wafer sleeve. Thus, a minimum amount of purge gas is introduced intothe outer portions of the reactor module, thereby minimizing the amountof undesirable deposition on surfaces outside of the interior of thereactor module. Deposition on the inner surfaces of the reactor moduleis further reduced by water cooling of the reactor module. A set ofexhaust outlet lines extends out of the top and bottom of the reactorframe. The exhaust gases comprise the purge gas, products from theepitaxial reaction within the reactor module, and unused reactant gases.

In an epitaxial reactor in which the process gases are confined within asmall region above the wafers, the percentage consumption of the processgases will be higher as the process gases flow from the inlet to theexhaust. This can cause the epitaxial deposition rate for wafers nearthe process gas inlet to be higher than for wafers nearer the exhaustoutlet lines due to a reduction in the reactant gas concentration withincreasing distance from the inlet.

Thus, another aspect of the present invention provides bi-directionalflow of process gases, enabling a “cross-flow” epitaxial depositionprocess. In this approach, the process gases first flow in onedirection, for example, downwards through the interior of the wafersleeve for a predetermined period. The direction of the process gas isthen reversed to the opposite direction, for example, upwards throughthe interior of the wafer sleeve for a similar predetermined period.This procedure can be repeated for a number of cycles during epitaxialdeposition on a set of wafers contained within the wafer sleeve, therebyaveraging out the deposition rates between the wafers at the top andbottom of the wafer sleeve. In addition, flow and exhaust can be setupfrom left to right and from right to left. In this arrangement, the gasflow is switched every 90 degrees thus closely simulating a rotarymotion of the wafer during deposition.

In a first embodiment of the overall system of the present invention,the epitaxial reactor may be integrated within a system comprising apreheat chamber, a single epitaxial deposition reactor, and a cool downchamber. In a second embodiment, two or more epitaxial depositionreactors may be employed in series, and combined with a preheat chamberand a cool down chamber. In this second embodiment, the epitaxialreactors each deposits part of the desired final film thickness. Thewafer sleeve then moves to the next reactor for another partialdeposition. For example, in a system comprising a preheat chamber, threeepitaxial reactors, and a cool down chamber, each of the epitaxialreactors could deposit approximately one third of the final desired filmthickness. During deposition within each of the three epitaxialreactors, the cross-flow deposition process could be employed to enhancedeposition uniformity. Thus, the deposition time per epitaxial reactorwould be one third that required for the single epitaxial reactor in thefirst embodiment. Assuming that the preheat and cool down times are lessthan one third of the total deposition time, this second embodimentcould provide a wafer throughput roughly three times higher than thethroughput of the first embodiment.

In a further embodiment of the present invention, a number of epitaxialreactors may be employed in series, with differing flow directions toachieve the desired overall film uniformity without the need forcross-flow processing within any of the epitaxial reactors. Thisapproach, which may be combined with a preheat chamber and a cool downchamber, enables simpler reactor chambers to be employed since eachreactor would need piping for only unidirectional process gas andexhaust flows.

Since the wafer sleeve of the present invention is heated by an array oflamps, a method of lamp sequencing may be employed to further enhancefilm deposition uniformities. In this method, the variation indeposition rate along a direction corresponding to the process gas flowsmay be made nearly linear by activation of the heating lamps for variousduty cycles less than 100%, thereby controlling the deposition ratethrough real-time control of the wafer temperatures in different partsof the wafer sleeves. Combining lamp sequencing with cross-flowprocessing could then enable relatively uniform overall deposition ratesto be obtained within and between wafers.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic side cross-sectional view of a prior art pancaketype epitaxial reactor.

FIG. 2 is a schematic side cross-sectional view of a prior art barreltype epitaxial reactor.

FIG. 3 is a schematic side cross-sectional view of a prior artSingle/Mini-Batch™ type epitaxial reactor.

FIG. 4 is a schematic outer side view of a lamp module of the presentinvention.

FIG. 5 is a schematic inner side view of the lamp module of FIG. 4.

FIG. 6 is a schematic vertical cross-sectional view of the lamp moduleof FIG. 4 through an outer cooling air plenum.

FIG. 7 is a schematic vertical cross-sectional view of the lamp moduleof FIG. 4 through the center cooling air plenum.

FIG. 8 is a schematic isometric view shown in partial cutaway of a wafersleeve of the present invention.

FIG. 9 is a schematic top view of the wafer sleeve of FIG. 8.

FIG. 10 is a schematic side view of a reactor frame of the presentinvention.

FIG. 11 is a schematic view of an illumination window of the presentinvention.

FIG. 12 is a schematic side view of the reactor frame of FIG. 10 withthe illumination window of FIG. 11 in place.

FIG. 13 is a schematic cross-section of a gas plenum.

FIG. 14 is a schematic top partial cross-sectional view of the reactionarea of the epitaxial reactor of FIG. 4.

FIG. 15 is a schematic view of a three module epitaxial reactor of thepresent invention with cross-flow processing.

FIGS. 16A-D are schematic views of the process gas and exhaust flows foran embodiment of the present invention with four different floworientations.

FIG. 17 is a schematic view of a five module epitaxial reactor of thepresent invention with three reactor modules using cross-flowprocessing.

FIG. 18 is a schematic side cross-sectional view of a single-passcross-flow reactor module of the present invention.

FIG. 19 is a graph of the epitaxial deposition rate against the verticalposition within the reactor module.

FIG. 20 is a schematic view of a six module epitaxial reactor of thepresent invention without cross-flow processing.

FIG. 21A is a schematic cross-sectional view of a single-pass reactormodule of the present invention at a first time within an epitaxialdeposition process utilizing a lamp sequencing procedure.

FIG. 21B is a schematic cross-sectional view of a single-pass reactormodule of the present invention at a time after the time illustrated inFIG. 21A.

FIG. 21C is a schematic cross-sectional view of a single-pass reactormodule of the present invention at a time after the time illustrated inFIG. 21B.

FIG. 22 is a graph illustrating how the lamp sequencing procedure shownin FIGS. 21A-C may linearize the variation in epitaxial deposition rateagainst the vertical position within the reactor module.

FIG. 23 is a graph of the epitaxial deposition rate against the verticalposition within the reactor module utilizing a lamp sequencing procedurecombined with cross-flow processing to improve uniformity.

FIG. 24 is a schematic cross-sectional view of a single-pass reactormodule of the present invention using varying lamp intensities from topto bottom of the lamp module in order to linearize the epitaxialdeposition rate.

DETAILED DESCRIPTION

One disadvantage of prior art epitaxial deposition systems for PV cellapplications is low throughput, measured in wafers per hour. Thus, itwould be desirable for an epitaxial reactor to process a large number ofwafers in parallel with the minimum deposition time practical to stillachieve the desired properties in the deposited films on PV solar cellwafers.

Accordingly, one aspect of the present invention includes an epitaxialreactor enabling the simultaneous deposition by chemical vapordeposition of films on a multiplicity of wafers, each supported by acarrier plate heated by an array of lamps mounted within a reflectorassembly. The epitaxial reactor of the present invention comprises oneor more lamp modules which illuminate a wafer sleeve contained within areactor frame which also supports the lamp modules. The followingfigures describe the lamp module, wafer sleeve, and reactor frameseparately. Next, the assembly of a reactor module is described,followed by the operation of the reactor module with respect toillumination, cooling, and process and purge gas flows. Variousconfigurations for the wafer sleeve are discussed, followed by differentembodiments comprising various numbers of reactors. Finally, amethodology for improving wafer-to-wafer deposition rates is discussed.

The overall reactor design can be summarized with respect to FIG. 14,which will be described later in more detail as will the other reactorparts. Wafers 920 are mounted on facing sides of two carrier plates 906within an interior volume 907 of a wafer sleeve (alternately called acarrier) generally arranged with one principal side extending verticallyand travelling horizontally to be stationarily placed within a reactionvolume 1503 of the reactor for the deposition process. Two lamp modules502 irradiate the outsides of the carrier plates 906 through windows1200. The carrier plates 906 are made out of material, such as siliconcarbide, which absorbs the visible and near infrared radiation of lampsand is heated by the radiation. Process gases, such as trichlorosilaneand hydrogen, flow vertically through the internal volume 907 of thesleeve 900 to epitaxially deposit material such as silicon on the wafers920. Typical reaction temperatures are typically in the range of 600 to1200° C.

Lamp Module

One disadvantage of the prior art epitaxial reactors heated byincandescent lamps is the consumable cost associated with the lamps.Typically, expensive tungsten-halogen lamps are used due to their highinfrared emission, making wafer heating more efficient. Tungsten-halogenlamps contain a coiled tungsten filament within a sealed tube containinga halogen gas. If the lamps are inadequately cooled, their lifetimes maybe substantially reduced, constituting an additional variable cost forthe wafer manufacturing process. Thus, it would be desirable to providea level of lamp cooling which will enable lamp lifetimes to be extended,thereby reducing the amortized lamp costs per PV cell wafer.Accordingly, one aspect of the present invention provides a lamp moduleallowing increased lifetime of the lamps.

The schematic outer side view of FIG. 4 shows a lamp module 400 of oneembodiment of the present invention. A lamp module structure 401 may beattached to the reactor frame 1000 (see FIG. 12) by a series of boltsthrough mounting holes. Cooling air for the lamp module 400 may enter acenter air plenum 412 through an inlet connection 413 leading to anentrance hole 414. The cooling air may exit the lamp module through twoouter air plenums 402 on either side of the center air plenum 412 andincluding exit holes 404 leading to exhaust connections 403. As isfamiliar to those skilled in the art, precise temperature monitoring andcontrol during epitaxial deposition may be important for obtaining theproper deposition rate, film composition, and other film properties.Active feedback from the pyrometers to the lamp control electronicsenables precise dynamic control of the wafer sleeve temperaturethroughput the epitaxial deposition process.

A cooling water inlet tube 420 leads to a network of channels within thelamp formed within the module structure 401 and then to a cooling waterexit tube 421. The exact arrangement of the network of cooling channelsmay be freely chosen. Adequate water cooling of the lamp module 400 canbe important in preserving lamp lifetimes, as well as ensuring that theillumination window (see FIG. 1) does not overheat, resulting in loss ofIR transmission efficiency as well as vacuum integrity within thereactor chamber. As is familiar to those skilled in the art, the coolingsystem may be equipped with a pressure sensor to detect any loss incoolant pressure. Should such a drop in pressure occur, all power to thelamps would be cutoff immediately to protect the reactor module andoperating personnel from any possible process gas leaks. The connectionwires 418, 419 for the opposing ends of the lamps extend out the sidesof the lamp module 400 as shown.

A schematic inner side view of the lamp module 400 of FIG. 4 is shown inFIG. 5. Eleven lamps 502 are shown in FIG. 5; however, the exact numberof the plural lamps 502 may be different. The lamps 502 extend linearlyand horizontally in parallel and have electrode bases on opposed endsfor their generally linearly extending coiled lamp filaments. Ahigh-temperature O-ring 501 for sealing against the outer surface of theillumination window 1200 (see FIG. 13) is contained within a groovemachined into the face of the lamp module structure 401. Each linearlyextending lamp 502 is located within and to one side of a reflector 503,which is typically coated with gold to maximize IR reflectivityuniformity and minimize oxidation. The lamps 502 in conjunction with thereflectors 503 present a substantially planar source of radiant heat.The lamps 502 may typically be tungsten-halogen lamps with maximumemission in the infrared around 1.2 μm wavelength and operating with afilament temperature in excess of 2000° K. Each lamp 502 has a base (notshown) at each of the ends of its transparent glass lamp tube connectedto opposed ends of the generally linearly extending filament and areremovably connected to respective electrical sockets. These sockets arewithin the water-cooled lamp module housing, and are maintained attemperatures below about 300° C. in order to prevent damage to the hightemperature O-rings which form an air-tight seal around the end of eachlamp socket in order to maintain the pressure of the cooling air for thelamps 502 within the lamp module 400. The lamps should be designed tominimize radiation near their ends.

A schematic vertical cross-sectional view A-A (see FIG. 4) through thelamp module of FIG. 4 at an outer cooling plenum is illustrated in FIG.6. An outlet air duct 610 connects to the outlet cone 403 to conductcooling air or other cooling gas for the lamps 502 out of the outletcooling plenum 402 at the back of the lamps 502 and their reflectors503. The outlet cooling plenum 402 connects to a multiplicity of airchannels 712 defined by walls 713 running parallel to and behind eachlamp 502. Plural air tubes 711 extending from each air channel 712 allowpassage of cooling air from the air channels 712 through the reflectors503 to each lamp 502. The cooling air from the inlet air plenum 412 issplit and flows in opposite directions along the linearly extendinglamps 502 to the two outlet cooling plenums 402 near the opposed ends ofthe lamps 502. Proper air cooling of the lamps 502 is important inmaximizing lamp lifetimes, thereby reducing the amortized lamp costs perwafer processed while increasing system uptime and reducing maintenancerequirements.

A schematic vertical cross-sectional view B-B through the midplane ofthe lamp module of FIG. 4 is illustrated in FIG. 7. An inlet air duct730 connects to the inlet cone 413 to conduct cooling air for the lamps502 into the inlet air plenum 412 at the back of the lamps 502 and theirreflectors 503 near the axial middle of the lamps 502.

The inlet air plenum 412 connects to a multiplicity of air channels 712running parallel to and behind each lamp 502. Plural air tubes 711extending from each air channel 712 allow passage of cooling air fromthe air channels 712 through the reflectors 503 to each lamp 502.

Wafer Sleeve

Another disadvantage of prior art epitaxial deposition systems is highconsumable costs arising from inefficient use of process gases. Thus, itwould be desirable for an epitaxial reactor to improve the use ofprocess gases in order to lower the volume of process gas needed todeposit a given film thickness. Yet another disadvantage of prior artepitaxial deposition systems is the large volume of the process chamberswhich must be filled by the process gases. This results in higher gasflow requirements and lower percentage utilization of the process gas.Often the inner surfaces of the process chambers are heated by the lampsor induction coils in order to heat the wafers, resulting in unwanteddeposition on the chamber walls. Thus, it would be desirable to maintainthe inner surfaces of the reaction chamber at a lower temperature thanthe wafers being heated to a reaction temperature and to minimize thevolume of the reactor zone for which process gas must be supplied.

Still another disadvantage of prior art epitaxial deposition systems isunwanted deposition on various surfaces on the inside walls of thereactor chamber. This unwanted deposition may produce severalundesirable consequences, including formation of particulates if thisunwanted deposition fails to adhere to the reactor chamber walls andflakes off, and added unproductive consumption of process gases, therebyincreasing variable costs for film growth, and requiring frequentopening up and cleaning of the reactor chamber. Thus, it would bedesirable for an epitaxial reactor to have minimal unwanted depositionon the walls of the reactor chamber, instead restricting most depositionto the wafer and possibly a small surrounding area of a wafer carrier.

Accordingly, another aspect of the invention includes a wafer sleevewhich mounts multiple wafers within an interior of the wafer sleeve,defines the flow of process gases within the wafer sleeve away from thewalls of the reactor, and which may be radiantly heated apart from thewalls of the reactor. That is, the reactor walls may be at asubstantially lower temperature than the wafers being processed and aregenerally not exposed to the deposition gases. In one embodiment, thesleeve includes two carrier plates having two respective generallyplanar and parallel principal surfaces on which the wafers are mountedto face a reaction zone within the sleeve. The lateral sides of thesleeve are closed and, in one embodiment, the gas delivery system atlast partially seals one or both of the ends of the sleeve to restrictthe flow of processing gas to the reaction zone inside the sleeve whilethe spent processing gas flows out the other end. However, thetransportable sleeve itself is preferred to have two open ends.

A schematic isometric view in partial cutaway of a wafer sleeve 900 ofone embodiment of the present invention is shown in FIG. 8. Two carrierplates 906 are detachably attached to two end caps 901, for example, bythreaded screws or bolts, clamps, springs, or spring-loaded clamps.Tongues 902 extending from each end cap 901 determine the spacingbetween the inner surfaces of the wafer carrier plates 906, whichtogether with the end caps 901 define a processing cavity generally openon two opposed ends. A multiplicity of wafers 920, some being visiblethrough a partial cutaway 910, are mounted with good thermal contact ontheir back sides to the wafer carrier plates 906 by some detachableattachment means such as, for example, shoulder screws 930 (see FIG. 9)screwed into the wafer carrier plates 906 and capturing the wafers 920with their shoulders. The end caps 901 may be incorporated into morecomplexly shaped carrier plates 906.

The invention allows efficient epitaxial deposition of silicon layers onsubstrates having at least a surface layer of crystalline silicon. Sucha substrate may be a monocrystalline silicon wafer, as used in theintegrated circuit industry, or have a crystalline layer of siliconattached to a non-silicon substrate. In some applications, the siliconlayer is deposited on a porous silicon layer of a mother wafer and thedeposited silicon film is then delaminated from the mother wafer andattached to a foreign substrate for further processing and mounting.

For insertion and removal of wafers 920 into and out of the wafer sleeve900, the wafer sleeve 900 can be disassembled, allowing easy access tothe inner surfaces of the wafer carrier plates 906. As illustrated inFIG. 9, a number of wafers can be attached in good thermal contact withthe inner surfaces of the wafer carrier plates 906. After all the wafers920 are attached, the wafer sleeve is then reassembled as shown in FIGS.8 and 9, placing the wafers to be processed in the interior of the wafersleeve 900.

The wafers 920 may be rectangular in view of their possible eventual useas part of panel of closely packed solar cells. The spacing between thetop process surfaces of the wafers 920 is generally equal to the spacingbetween the inner surfaces of the wafer carrier plates 906 minus thethicknesses of the two wafers 920. By making the spacing between theinner surfaces of the carrier plates 906 in the range from 2 to 8 mm,more generally 2 mm to 2 cm, the present invention enables the creationof a very small reaction volume 907. To accommodate multiple wafers in atwo-dimensional array, the principal walls of the sleeve 900, that is,the carrier plates 906, preferably have lateral dimensions of 40 cm ormore so that the aspect ratio of the lateral dimensions to thickness ofthe interior of the sleeve 900 is at least 20:1 and preferably greaterthan 40:1. As the process gases flow within this small reaction volumebetween the wafer carrier plates 906, the boundary layers above eachwafer may comprise a substantial fraction of the total reaction volume.Because gas velocities decrease within boundary layers, the reactiontime of the process gases with the heated wafers 920 is therebyincreased, leading to improved reaction efficiencies. End caps 901 withvarious tongue 902 widths may be used to select different spacingsbetween the inner surfaces of the wafer carrier plates 906 to optimizethe reactor module for various epitaxial deposition processes and gasmixtures. FIG. 9 is a schematic top view of the wafer sleeve of FIG. 8,showing shoulder screws 930 clamping the wafers 920 in good thermalcontact with the wafer carrier plates 906.

Reactor Frame, Reactor Chamber, and Cross Flow Processing

A disadvantage of prior art epitaxial deposition systems is the need forrotary motions of the wafer susceptor or wafer carrier within thereactor chamber in order to achieve the desired uniformities of filmthickness and resistivity. As is well known in the art, mechanicalmotions may create a number of design and operational difficultieswithin chambers containing hot reactive gases. Thus, it would bedesirable for an epitaxial reactor to achieve desired process filmuniformities without the need for rotary or other types of motions ofthe wafers during processing.

Accordingly, another aspect of the invention includes a reaction chamberallowinging alternately flowing process gases in opposite oranti-parallel directions across the wafers, preferably stationarywafers.

A schematic side view of a reactor frame 1000 of the present inventionis shown in FIG. 10. The wafer sleeve 900 containing the wafers (notshown) on which an epitaxial film is to be deposited is contained withina reactor chamber 1001. The reactor chamber 1001 includes a centralopening formed by four interior walls 1003 in the reactor frame 1000 andby two illumination windows 1200 (see FIG. 11) fitting within recesses1002 on opposed sides of the reactor frame 1000. Cooling water for thereactor frame 1000, which is preferably formed of a metal, entersthrough an inlet line 1031, then flows through a network of coolingchannels (not shown) within the reactor frame 1000, and finally exitsthrough an outlet tube 1032. Adequate cooling of the reactor frame 1000serves to maintain the walls of the reactor chamber 1001 at low enoughtemperatures to minimize undesirable epitaxial deposition on the frame1000. An outer high temperature O-ring 1011 and an inner hightemperature O-ring 1010 seal against the inner surface of theillumination window 1200 to form a differentially-pumped seal betweenthe interior of the reactor chamber 1001 and the air. Differentialpumping connections 1012 lead to openings 1013 between the two O-rings1010, 1011.

Two exhaust lines 1014 extend out the top of the reactor frame 1000, andtwo more exhaust lines 1024 extend out the bottom of the reactor frame1000. One purge gas inlet line 1016 connects with the top of the reactorframe 1000, and another purge gas inlet line 1026 connects with thebottom of the reactor frame 1000. Two process gas inlet lines 1015connect with the top of the reactor frame 1000 and two more process gasinlet lines 1025 connect with the bottom of the reactor frame 1000. Ahorizontally extending upper process plenum 1080 is mounted to theinterior wall 1003 at the top of the reactor chamber 1001. The processgas lines 1015 and exhaust lines 1014 at the top of the reactor frame1000 are connected to the interior of the upper process plenum 1080 andthe purge gas line 1016 is directed to the exterior of the upper processplenum 1080 as described below in FIG. 13. Similarly, a lower plenum1081 is mounted to the interior wall 1003 at the bottom of the reactorchamber 1001. The process gas lines 1025 and exhaust lines 1024 at thebottom of the reactor frame 1000 are connected to the interior of thelower process plenum 1081 and the purge gas line 1026 are directed tothe exterior as described below in FIG. 13. The upper process plenum1080 is positioned within the reactor chamber 1001 to have a small andperhaps minimal clearance between the lower surface of the upper processplenum 1080 and the upper surface of the wafer sleeve 900 to provide asomewhat leaky seal between them, thereby minimizing process gas leakagefrom within the sleeve 900 against a pressure differential (see FIG. 13)of the process gas being held at a lower pressure than the purge gas.However, in one embodiment, the leaky seal provides an exhaust pumpingpath for otherwise generally stagnant purge gas outside the wafer sleeve900. Similarly, a lower plenum 1081 is positioned within the reactorchamber 1001 to have a minimal clearance between the upper surface ofthe lower plenum 1081 and the lower surface of the wafer sleeve 900,thereby minimizing gas leakage while perhaps providing an exhaust pathfor the purge gas under a pressure differential (see FIG. 13).

Valves and gas supplies or exhaust ports are connected to the inlet andoutlet ports so that the gas flows can be reversed although it ispossible to not reverse the in flow of the purge gas.

Further, the process gas may be switched during processing to providingdifferent doping types for n-type, intrinsic, and p-type silicon orother semiconductor, for example, adding borane or phosphine totrichlorosilane, or to provide other process gases such as hydrogen toaffect the morphology of the deposited material.

The functioning of the purge and process gas inlets and the exhaust gasoutlets during a cross-flow epitaxial deposition process is as follows.As described with reference to FIG. 15, the epitaxial reactor 1804 maybe operated using a bi-directional process gas flow procedure, called“cross-flow” processing. In a first phase of cross-flow processing, theprocess gases used for the CVD precursors flow downwards from the topprocess gas inlets 1015 of FIG. 10 at the top of the reactor frame 1000first into the upper process plenum 1080 and then into the wafer sleeve900. The process gases from the inlets 1015 are directed by the upperprocess plenum 1080 preferentially into the interior of the wafer sleeve900 between its wafer carrier plates 906 to maximize utilization of theprocess gas. At the same time, purge gas, typically hydrogen, flowsdownwards into the reactor chamber 1001 from the top purge gas inletline 1016 to the exterior of the wafer sleeve 900. The purge gas isdirected preferentially outside the wafer carrier plates 906 of thewafer sleeve 900 to reduce or eliminate deposition on the window andwalls of the reactor chamber 1001. The pressure of the purge gas outsideof the wafer sleeve may be adjusted to exceed the pressure of thereactant gases within the wafer sleeve 900, thereby ensuring minimalleakage of reactant gases out of the interior volume of the wafer sleeve900 and allowing the purge gas to be exhausted through the leaky sealsinto the interior of the plenums, particularly the outlet plenum beingpumped. In this first phase, product gases and unused reactant gasesfrom the interior of the wafer sleeve 900 flow into the lower processplenum 1081 and the purge gas flows from the portion of the reactionchamber 1001 exterior to the wafer sleeve 900 through the leaky sealinto the lower process plenum 1081. The product gas, unused process gas,and purge gas then flow into the open pumped exhaust lines 1024 on thebottom of the reactor frame 1000. The bottom purge gas 1026, process gaslines 1025, and top exhaust lines 1014 are valved off during the firstphase of epitaxial deposition.

In a second phase of cross-flow processing, the process gases flowupwards from the bottom process gas inlets 1025 first into the lowerprocess plenum 1081 and then into the wafer sleeve 900. As for the firstphase of cross-flow processing described above, the process gases fromthe bottom process gas inlets 1025 are directed preferentially into theinterior of the wafer sleeve 900 by the lower process plenum 1081 tomaximize the efficiency of process gas usage. At the same time, purgegas, typically hydrogen, flows from the bottom purge gas inlet line 1026upwards into the reactor chamber 1001 exterior to the wafer sleeve 900.The purge gas is directed preferentially outside the wafer sleeve 900 toreduce or eliminate deposition on the window and walls of the reactorchamber 1001, as in the first phase described above. In this secondphase, product gases and unused reactant gases flow from the interior ofthe wafer sleeve 900 into the upper process plenum 1080 and purge gasfrom the portion of the reactor chamber 1001 exterior to the wafersleeve 900 flow through the leaky seal into upper process plenum 1088.The product and unused processes gases and the purge gas then flows intothe exhaust lines 1014 on the top of the reactor frame 1000. The toppurge gas lines 1016, process gas line 1015, bottom exhaust lines 1024are valved off during the second phase of epitaxial deposition.

A schematic view of the illumination window 1200 of the presentinvention is illustrated in FIG. 11. Typically, the illumination window1200 can be quartz, approximately 10 mm thick with a non-clear region1202 surrounding a central clear region 1201. The central clear region1201 may be sized to approximately match the dimensions of thelamp-heated sides of the wafer sleeve 900. The outer non-clear region1202 may be sized to cover the high temperature O-rings 1010, 1011within the reactor frame 1000 (see FIG. 12), thereby protecting theO-rings 1010, 1011 against heating from the lamp module 400. There areseveral alternatives for the construction of the non-clear region 1202.It may be covered with a reflective substance to reflect anyillumination from the lamp module 400 which strikes the non-clear region1202. Alternatively, the non-clear region 1202 may be made fromtranslucent quartz which will reflect some illumination and scatter someillumination from the lamp module 400.

The schematic side view of FIG. 12 shows the reactor frame 1000 of FIG.10 with an illumination window 1200 installed into the recess 1002 inthe reactor frame 1000. The purpose for the non-clear region 1202 ofillumination window 1200 can be seen from FIG. 12 where the non-clearregion 1202 shields the high-temperature O-rings 1010, 1011 from thelight emitted from the lamps 502 in the lamp module 400.

Gas Distribution Plenums in the Reactor Frame

As described above for FIG. 10, two process plenums 1080, 1081 aremounted within the reactor chamber 1001 to facilitate even distributionof process gases into the interior of the wafer sleeve 900 and to removegases from the reactor chamber 1001. FIG. 13 is a schematiccross-section of the upper plenum 1080 as well as the top of a wafersleeve 900. The lower process plenum 1081 may be similar or identical,but would be typically mounted in an inverted configuration comparedwith the upper process plenum 1080 as shown in FIG. 13. The followingdiscussion relates to the upper process plenum 1080 but is equallyapplicable to the lower process plenum 1081. The process gas lines 1015(not shown here) are connected through connection tubes 3001 andopenings 3002 to an upper distribution plenum 3003 formed by plenumstructure 3012. A first multiplicity of holes 3004 are distributed alongthe length of the upper distribution plenum structure 3012, extendingacross the upper width of the wafer sleeve 900 as shown in FIG. 10, andenabling even filling of the interior 3005 of tube 3013 with processgases. A second multiplicity of holes 3006, also extending across theupper width of the wafer sleeve 900, extend out from the bottom of thetube 3013, enabling process gases 3051 to flow into the interior 907 ofthe wafer sleeve 900.

Purge gases 3050 flowing into the reactor chamber 1001 from feed line1016 flow around the upper plenum 1080 as shown. The upper plenum 1080may have a flange structure 3007 to reduce leakage into the interior ofthe wafer sleeve 900 through the gap 3010 formed between the flange 3007and the upper edges of the wafer carrier plates 906. Operation of thelower plenum 1081 may be essentially the same as described above, exceptusing the corresponding process gas 1025, purge gas 1026 and exhaustlines 1024 at the bottom of the reactor frame 1000.

One or more wide exhaust ports are connected to the interior 3005 of thetube 3001 and pump the reaction volume within the wafer sleeve 900through the series of wide holes 3006. This dual use of the processplenum requires that the process supply and exhaust be alternatelyperformed upon each of the opposed process plenums.

Although it is possible to adapt the reactor chamber 1001 to operate atlow pressures, good epitaxial deposition is accomplished by nearatmospheric operation, but with pressure differentials sufficient tocontrol the gas flows.

With the cross-flow process during downwards gas flow, when the upperprocess plenum 1080 supplies process gases into the interior 907 of thewafer sleeve 900, the lower process plenum 1081 provides an exhaust forremoving gases from the interior 907 of the wafer sleeve 900 and therest of the reactor chamber 1001. During upwards gas flow, the lowerplenum 1081 supplies process gases into the interior 907 of the wafersleeve 900 and the upper plenum provides an exhaust for removing gasesfrom the interior 907 of the wafer sleeve 900.

Epitaxial Reactor with Two Lamp Modules

FIG. 14 is a schematic partial close-up top cross-sectional view C-C ofthe reaction area of the epitaxial reactor of FIG. 10. As describedabove in FIG. 10, process gases are preferentially directed into theinterior volume 907 of the wafer sleeve 900, which is enclosed by thecarrier plates 906 and the end caps 901. Purge gases are preferentiallydirected into the interior volume 1503 within the reactor chamber 1001surrounding the wafer sleeve 900. As described for FIG. 13, the pressureof the purge gases outside of the wafer sleeve may be adjusted to exceedthe pressure of the process gases within the wafer sleeve 900, therebyensuring minimal leakage of process gases out of the interior volume 907of the wafer sleeve 900. The volume 1503 may be sealed by slit valves(see, for example, the slit valves 1803 and 1805 in FIG. 15), therebyforming a closed volume surrounding the wafer sleeve 900. Alternatively,volume 1503 may essentially extend into neighboring epitaxial reactorchambers as shown, for example, in FIG. 20 where the epitaxial reactors2304, 2306 and 2308 are separated by pass-through chambers 2305 and2307.

The illumination windows 1200 on both sides of the wafer sleeve 900 formbarriers between the reactor chamber 1001 and the air 1502 or othercooling gas surrounding the lamps 502, allowing the illumination 1501from the lamps 502 to pass into the reaction chamber 1001.

Three Module Epitaxial Reactor with Cross-Flow Processing

A three module epitaxial reactor 1800 of one embodiment of the presentinvention is illustrated schematically in FIG. 15. A wafer sleeve (notshown) loaded with wafers ready for processing can be loaded in thedirection 1820 through a reactor entrance slit valve 1801 into a preheatchamber 1802. The preheat chamber can use any number of methods ofheating the wafer sleeve such as lamps, resistive elements, or inductionheating. The profile of temperature with time for the wafer sleevewithin the preheat chamber 1802 should be fast enough to keep up withthe deposition times of films in the subsequent epitaxial reactorchamber(s), but slow enough to avoid thermally-induced stresses in thewafers within the wafer sleeve. The preheat chamber 1802 may have astructure simplified from that of the reactor chamber but having twolamp modules to radiantly heat the wafer sleeve. However, simplerheating apparatus are possible, such as resistively or inductivelyheated chambers.

After the wafer sleeve has reached the proper temperature, a preheatchamber slit valve 1803 is opened to permit transfer of the wafer sleevefrom the preheat chamber 1802 into the epitaxial reactor 1804. Thepreheat chamber slit valve 1803 would then be closed. A reactor slitvalve 1805 must also have been closed by this time. Now, an epitaxialdeposition process is initiated within the reactor 1804 upon thestationary wafer sleeve 900 until the desired film thickness has beendeposited on the wafers within the wafer sleeve 900 located in thereactor 1804. Bi-directional arrows 1831 illustrate the two directionsof process gas flow for a cross-flow epitaxial process within thereactor 1804. As discussed below, due to reactant gas depletion effects,a cross-flow epitaxial deposition process may be required within reactor1804 in order to achieve the required film thickness and resistivityuniformities within and between the wafers contained in the wafersleeve.

Next, the reactor slit valve 1805 is opened to permit transfer of thehot wafer sleeve into a cool down chamber 1806, after which the reactorslit valve 1805 would be closed. The cool down chamber 1806 may have astructure greatly simplified from that of the reactor 1804, for example,having two water-cooled frames facing the wafer sleeve 900. An exit slitvalve 1807 would also already have been closed at this time to avoidpremature exposure of the wafer sleeve to the air before adequatecooling down has occurred. The wafer sleeve then remains in the cooldown chamber 1806 until a low enough temperature for removal has beenachieved, after which the exit slit valve 1807 is opened and the wafersleeve is removed from the epitaxial reactor system. For optimumthroughput, more than one wafer sleeve may be in transit through theepitaxial reactor system at any one time. For example, a first wafersleeve might be cooling off in the cool down chamber 1806, while asecond wafer sleeve is undergoing epitaxial deposition in the reactor1804, and a third wafer sleeve is heating up in the preheat chamber1802. Note that for this first embodiment, the average processing timefor the wafers in the wafer sleeve is equal to the time to deposit theentire required film thickness in the single reactor chamber 1804.

The processing within the reactor 1804 may vary over a process cycle inorder to provide a graded structure, for example, of semiconductordopants.

The wafer sleeves may be transported into and through the series ofchambers and reactors by a transport mechanism capable ofhigh-temperature operation and of placing the sleeves at predeterminedpositions with the chambers or reactors. For example, silicon carbidebearings may be used for movable support and vertical alignment of thewafer sleeves even near and into the hot zone. The drive mechanism maybe stored in cooler regions of the chambers or reactors duringhigh-temperature processing, for example, away from the lamps, forexample, adjacent the slit valves. When sleeve movement is required, thedrive mechanism can engage cooler portions of the sleeve or can wait forpartial cooling of the chambers or reactors before extending movementarms or other mechanisms to engage the sleeve to move it to its nextposition.

Epitaxial Reactor with Cross-Flow Processing Along Four ApproximatelyOrthogonal Directions

In the embodiment shown in FIG. 15, the process gases alternate betweendownwards and upwards flow. However, in some cases, a degree ofleft-right asymmetry may remain in the film thickness and resistivityuniformities achieved in such a bi-directional deposition process. FIGS.16A-D schematically illustrate a four-step process which could reduce oreliminate this undesirable deposition uniformity. FIGS. 16A-D illustratethe same four wafers 2001 mounted in good thermal contact with a wafersleeve 2002 within a reaction chamber (not shown). FIG. 16A and FIG. 16Ccorrespond to the first and second steps described in FIG. 15,respectively.

For FIG. 16A, the reactant and purge gases 2011 are admitted to thereaction chamber at the top, while the process gas exhaust 2012 emergefrom the bottom of the reaction chamber. For FIG. 16C, the reactant andpurge gases 2031 are admitted to the reaction chamber at the bottom,while the process gas exhaust 2032 would emerge from the top of thereaction chamber. The key difference between FIG. 15 and FIGS. 16A-D isthe addition of two additional deposition steps in FIGS. 16B and 16D forwhich the process gas and exhaust gas directions are approximatelyorthogonal to the directions in FIGS. 16A and 16C. For FIG. 16B, thereactant and purge gases 2021 would be admitted to the reaction chamberfrom the right, while the process gas exhaust 2022 would emerge from theleft of the reaction chamber. For FIG. 16D, the reactant and purge gases2041 would be admitted to the reaction chamber from the left, while theprocess gas exhaust 2042 would emerge from the right of the reactionchamber.

A potential advantage of implementing this four-directional depositionprocess over the bi-directional process illustrated in FIG. 15 is theopportunity to further enhance the film thickness and resistivityuniformities. The reason for this is that a four-directional depositionprocess upon stationary wafers will more closely approximate adeposition process in which the wafers are continually rotated duringdeposition, as was illustrated for all three prior art systems in FIGS.1-3.

Five Module Epitaxial Reactor with Cross-Flow Processing

A five module epitaxial reactor of another embodiment of the presentinvention is illustrated in FIG. 17. A wafer sleeve (not shown) loadedwith wafers ready for processing is loaded in the direction 1920 throughan entrance slit valve 1901 into a preheat chamber 1902. Entrance slitvalve 1901 is then closed. The preheat chamber slit valve 1903 must alsoalready have been closed at this point. The wafer sleeve then undergoesa preheat process up to a pre-determined temperature suitable forintroduction into a first epitaxial reactor chamber 1904. After thewafer sleeve has reached the proper temperature, the preheat chamberslit valve 1903 is opened to permit transfer of the wafer sleeve fromthe preheat chamber 1902 into the first epitaxial reactor 1904. Thepreheat chamber slit valve 1903 is then closed. A first reactor slitvalve 1905 may also be closed at this time. Now, a first epitaxialdeposition process is initiated within the first epitaxial reactor 1904until approximately a third of the desired final film thickness has beendeposited on the wafers within the wafer sleeve. Next, the first reactorslit valve 1905 is opened to permit transfer of the wafer sleeve intothe second epitaxial reactor 1906, after which the first reactor slitvalve 1905 may be closed. The second reactor slit valve 1907 may also beclosed at this time. A second epitaxial deposition process is theninitiated within a second reactor 1906 until approximately another thirdof the desired final film thickness has been deposited on the waferswithin the wafer sleeve. This process repeats again for a third reactor1908, having a third reactor slit valve 1909, depositing the final thirdof the total required film thickness on the wafers within the wafersleeve. If desired, the three depositions may produce the samecomposition, different dopings, different compositions, or a gradedcomposition.

The third reactor slit valve 1909 is then opened to permit transfer ofthe hot wafer sleeve into the cool down chamber 1910, after which thethird reactor slit valve 1909 is closed. An exit slit valve 1911 musthave already been closed at this time to prevent premature venting ofthe wafer sleeve to air. The wafer sleeve then remains in the cool downchamber 1910 until a low enough temperature for removal has beenachieved, after which the exit slit valve 1911 is opened and the wafersleeve is removed from the epitaxial reactor system. As for theembodiment illustrated in FIG. 15, more than one wafer sleeve may be intransit through the epitaxial reactor system at any one time to achieveoptimum throughput. In particular, each of the epitaxial reactors 1904,1906, 1906 may be simultaneously depositing nearly equally thick layersupon three sequentially presented sets of wafers.

A variant on the design of the epitaxial reactor of FIG. 17 is toreplace one or both of the reactor slit valves 1905 and 1907 withvalve-free pass-through chambers or passages. This may be possible incases where the same film composition is being deposited in all threereactors 1904, 1906 and 1908, in which case there is no possibility ofcross-contamination between chambers since the process gases and theirrelative concentrations are the same. This variant may have theadvantage of lower costs as well as slightly higher throughputs due tothe elimination of valve closing and opening times.

In both the configuration shown in FIG. 17 and the variant withpass-through chambers, cross-flow processing within the three epitaxialreactors is illustrated by the arrows 1931-1933. However, in multipleepitaxial reactors, it is possible to implement some of the reactorswithout cross flow since counterflow may be introduced between chambers.For cases with odd numbers of reactor chambers, cross-flow processingmay generally be necessary in at least one chamber to equalize thedeposition thickness occurring using gas flow in each direction. Forexample, if chamber 1904 has vertical downwards process gas flows, andchamber 1908 has vertical upwards process gas flows, then chamber 1906might need cross-flow processing with equal amounts of deposition in theupwards and downwards gas flow directions. An advantage of thisalternative configuration is the simplification of process gas andexhaust piping for reactor chambers 1904, 1908 since only unidirectionalflows would be necessary in these two chambers 1904, 1908. The processgas piping for reactor chamber 1906 in this example would remain thesame, however.

A schematic side cross-sectional view of a single-pass cross-flowreactor module of the present invention is shown in FIG. 18. As theprocess gas 1960 flows downwards between the wafer carrier plates 906and wafers 920, boundary layer effects at the surface of each wafer 920will reduce the velocity of the process gas parallel to the wafersurface, thereby increasing the time available for the epitaxial CVDreaction to occur. As the process gases react on the surfaces of wafers920, the concentration of process gases will decrease in comparison withthe amount of product gases. Thus for wafers 1961 which are farther thanthe source of process gases, there may be a reduced deposition rate. Thecross-flow process is designed to reduce this effect, giving better filmthickness and resistivity uniformities.

Six Module Epitaxial Reactor with Optional Cross-Flow Processing

A six module epitaxial reactor of still another embodiment of thepresent invention is illustrated in FIG. 20. In this embodiment, fourepitaxial reactors 2304, 2306, 2308, and 2310 are separated bypass-through chambers 2305, 2307 and 2309, not slit valves as was thecase for the embodiments illustrated in FIGS. 15 and 17. A wafer sleeve(not shown) containing wafers ready for processing is loaded in thedirection 2340 through an entrance slit valve 2301 into a preheatchamber 2302. A preheat chamber slit valve 2303 must already be closedat this point. After the wafer sleeve has reached the propertemperature, the preheat chamber slit valve 2303 is opened to permittransfer of the wafer sleeve from the preheat chamber 2302 into thefirst epitaxial reactor 2304. The preheat chamber slit valve 2303 isthen closed. Now, a first epitaxial deposition process is initiated uponthe stationary sleeve within the first reactor 2304 until approximatelya fourth of the desired final film thickness has been deposited on thewafers within the wafer sleeve. Concurrently, a second wafer sleeve maybe loaded into the preheat chamber 2302 and preheated therein accordingto the same process accorded the first wafer sleeve. Next, the firstwafer sleeve is transferred through the first pass-through chamber 2305into the second epitaxial reactor 2306. A second epitaxial depositionprocess is then initiated uon the stationary sleeve within the secondreactor 2306 until approximately another fourth of the desired finalfilm thickness has been deposited on the wafers within the wafer sleeve.Concurrently, the second wafer sleeve is transferred from the preheatchamber 2302 to the first epitaxial reactor 230. This process repeatsagain for the third epitaxial reactor 2308 and the fourth epitaxialreactor 2310, depositing the last two quarters of the desired final filmthickness on the wafers within the wafer sleeve. During all depositionprocesses within reactors 2304, 2306, 2308, and 2310, the reactor slitvalve 2311 is closed.

After completion of deposition within the fourth reactor 2310, thefourth reactor slit valve 2311 is opened to permit transfer of the hotwafer sleeve into the cool down chamber 2312, after which the fourthreactor slit valve 2311 is closed. The wafer sleeve then remains in thecool down chamber 2312 until a low enough temperature for removal hasbeen achieved, after which the exit slit valve 2313 is opened and thewafer sleeve is removed from the epitaxial reactor system. Meanwhilemultiple wafer sleeves are being processed in the queue. As for theearlier embodiments illustrated in FIGS. 15 and 17, more than one wafersleeve may be in transit through the epitaxial reactor system at any onetime to achieve optimum throughput.

Note that since the epitaxial deposition system illustrated in FIG. 20has an even number of epitaxial reactor chambers, it may be unnecessaryto employ cross-flow processing in any of the epitaxial reactors 2304,2306, 2308, and 2310 to achieve the desired deposition uniformities. Inconfigurations with an odd number of epitaxial reactors, typically atleast one epitaxial reactor will benefit from cross-flow processing inorder to achieve equal amounts of deposition in each of the two processgas flow directions. The arrows 2341 in reactor 2304 show that theprocess gases and purge gas need only enter from the bottom and that theexhaust gases need only be exhausted out the top, thereby substantiallysimplifying the piping configuration for epitaxial reactor 2304.Similarly, reactor 2306 is shown with arrows 2342 illustrating avertical downwards process gas and exhaust flow, with similarimplications for simplifying the gas and exhaust piping as was the casefor reactor 2304. Reactor 2308 has the same flow direction 2343 asreactor 2304, and reactor 2310 has the same flow direction 2344 asreactor 2306. Thus two reactors have each possible flow direction formaximized deposition uniformity without the need for cross-flowprocessing in any epitaxial reaction chamber. This is in contrast to thelikely situation for the epitaxial deposition system illustrated in FIG.17 with an odd number of epitaxial reactors.

Improving Deposition Uniformity Using Cross-Flow Processing

A graph of the epitaxial deposition rate 2102 against the verticalposition 2101 within the reactor module is shown in FIG. 19. Asdiscussed above for FIG. 18, when the process gases are flowingvertically downwards within the wafer sleeve, the deposition rate willbe higher for wafers nearer the top of the wafer sleeve and lower forwafers nearer the bottom of the wafer sleeve, as shown by theshort-dashed curve 2103. Conversely, when the process gases are flowingvertically upwards within the wafer sleeve, the deposition rate will behigher for wafers nearer the bottom of the wafer sleeve and lower forwafers nearer the top of the wafer sleeve, as shown by the long-dashedcurve 2104. Since the two deposition rate curves 2103, 2104 areindependent, i.e., there is no interaction between the two operatingmodes, and if the two modes are employed equal amounts of time, the netdeposition rate on the wafers within the wafer sleeve will be thearithmetic mean 2105 of the two curves 2103, 2104. Note that the meandeposition rate curve 2105 shows a greatly improved uniformity top tobottom within the wafer sleeve, however, complete top-to-bottomuniformity would only be achievable if the individual curves are roughlylinear, which is not generally the case.

Improving Deposition Uniformity Using Lamp Sequencing

Observation of the schematic top-down process flow deposition rate curve2103 in FIG. 19 shows that the deposition rate is highest at the top ofthe reactor, near the process gas inlet where the concentration ofreactants is highest. Progressing downwards, the deposition ratedecreases as expected since the concentrations of reactants will bedepleted by the deposition processes on the wafers above. If thedecrease in deposition rate were linear, however, i.e., if the top-downcurve 2103 and the bottom-up curve 2104 were straight lines, then thecombined average deposition rate curve 2105 might be near to a highlyuniform constant deposition rate independent of vertical position withinthe wafer sleeve. As shown in FIG. 19, however, since the top-down curve2103 and the bottom-up curve 2104 both tend to beconcave upwards, theaverage deposition rate curve 2105 is also concave, giving higheraverage deposition rates near the top and bottom of the reactor. Tofurther improve the film thickness and resistivity uniformities, anadditional process called “lamp sequencing” may be employed to furtherimprove within wafer and wafer-to-wafer uniformities by real-timecontrol of the illumination intensities of the lamps within the lampmodules used to heat the wafer sleeve. A lamp sequencing procedurewithin a single pass reactor module of the present invention is shown inthe schematic cross-sectional views of FIGS. 21A-C.

All of the curves in FIG. 19 assume that all the lamps 2403 are on allthe time, uniformly heating the wafer carrier plates 2430 and thus thewafers 2431 attached thereto. If the lamps 2403 are configured withindependent controls and power supplies, however, this need not be thecase, as illustrated in FIGS. 21A-B. To “straighten” the top-down andbottom-up deposition curves in FIG. 19, the deposition rates near thetops and bottoms of the wafer sleeve may be changed with respect to thedeposition rate at the center of the wafer sleeve be thermally varyingthe radiant intensity across the vertical direction by differentiallypowering the different lamps 2403. On the other hand, conventional lamps2403 produce a uniform radiant intensity along their respective lengths.

The view in FIG. 21A is near the beginning or other point of waferprocessing. Two arrays of independently controllable lamps 2403 aremounted facing towards the wafer sleeve comprising two wafer carrierplates 2430, with each array of lamps mounted within a respectivereflector assembly 2401. The wafers 2431 are attached with good thermalcontact to the wafer carrier plates 2430. The process gas flow direction2440 is shown downwards although the lamp sequencing procedure worksequally well with an upward process gas flow direction. High intensityillumination 2441 from the four center lamps 2403 within the lampmodule, that is, the most distant lamps from the two source of processgas, is shown preferentially heating the center region of the wafersleeve. Since the rates of epitaxial deposition are highly temperaturesensitive, reducing the temperatures of the tops and bottoms of thewafer carrier plates 2430 can substantially affect the deposition ratesfor the wafers 2431 near the tops and bottoms of the wafer carrierplates 2430 compared with the deposition rates near the centers of thewafer carrier plates 2430.

At a later or different period during deposition, some lamps nearer thetop and bottom of the wafer carrier plates 2430 nearer the sources ofprocess gas may be turned on as shown in FIG. 21B, where illumination2441 from the center four lamps may continue at the same level as inFIG. 21A while additional illumination 2450 has been added to increasethe energy flux into the upper and lower portions of the wafer carrierplates 2430. Finally, or in a different period during deposition, alllamps 2403 may be turned on as illustrated in FIG. 21C, whereillumination 2460 from the top and bottom lamps 2430 has been added tothe pre-existing illumination 2441 and 2450 to now fully heat the wafercarrier plates 2430 from top to bottom. That is, the linear distributionof radiation across the vertical axis of the wafers may be varied duringdeposition but the radiation remains substantially constant in thehorizontal direction at a given vertical position because of the linearnature of the lamps.

FIG. 22 is a graph illustrating how the lamp sequencing procedure shownin FIGS. 21A-C may modify the epitaxial deposition rate against thevertical position within the wafer sleeve. Short-dashed curve 2503 isthe same as the short-dashed top-down process gas flow curve 2103 inFIG. 19. The downward arrows 2504 at the left represent the decreaseddeposition rate near the top of the wafer sleeve due to the decreasedduty cycle of the top lamp lamps 2403 relative to the center lamps 2403while the downward arrows 2505 at the right represent the decreaseddeposition rate near the bottom of the wafer sleeve due to the decreasedduty cycle of the bottom lamps 2403. With proper calibration of the lampsequencing procedure of FIGS. 21A-C, the linearity of the adjusteddeposition rate 2506 may be improved. For each type of depositionprocess, the proper lamp sequencing procedure must be determined sincerates of process gas consumption with flow across the wafers may differ.Note that although lamp sequencing may improve the linearity of thedeposition rate as a function of distance from the top of the reactor,it alone is often insufficient to achieve process uniformity. For this,cross-flow processing may also be necessary in conjunction with lampsequencing as illustrated in FIG. 23.

A graph is shown in FIG. 23 of the epitaxial deposition rate 2602against the vertical position 2601 within the wafer sleeve utilizing alamp sequencing procedure combined with cross-flow processing to improveuniformity. The deposition rate as a function of vertical positionwithin the wafer sleeve for top-down process gas and exhaust flows isshown as a short-dashed curve 2603 descending from the upper left. Thedeposition rate for bottom-up flows is shown as a long-dashed curve 2604ascending from the lower left. Note that lamp sequencing has been usedto linearize both these curves. By employing cross-flow processing forequal times, the average deposition rate is the arithmetic mean 2605 ofthe top-down curve 2603 and the bottom-up curve 2304. Comparison of thisaverage deposition rate curve 2605 with the concave average depositionrate curve 2105 in FIG. 19 shows the possible improvement in uniformityachievable with a combination of both lamp sequencing and cross-flowprocessing.

Alternative Method of Lamp Sequencing

The lamp sequencing method described in FIGS. 21A-C employed an on/offlamp control methodology to linearize the deposition rate variation fromthe top to the bottom of the wafer sleeve. An alternative approach fordeposition rate linearization is illustrated in FIG. 24. Two arrays ofindependently controllable lamps 2803 are mounted within respectivereflector assemblies 2801 facing towards the wafer sleeve and its twowafer carrier plates 2830. The wafers 2803 are attached with goodthermal contact to the wafer carrier plates 2830. The process gas flowdirection 2840 is shown downwards, although the alternative lampsequencing procedure works equally well with an upward process gas flowdirection. The difference between the lamp sequencing proceduredescribed in this section compared with the sequence in FIGS. 21A-C isthe use of variable light intensities instead of on/off lamp control bypowering different lamps in the array with variable levels of finitepower.

In the example of FIG. 24, the outer two lamps have a low illuminationlevel 2841, the next two lamps inwards have a slightly higherillumination level 2842, the next two lamps inwards have an even higherillumination level 2843, while the center two lamps have the highestillumination level 2844 of all. This illumination profile will cause thevertical centers of the wafer carrier plates 2830 to be somewhat hotterthan the tops and bottoms. In this case, in contrast with FIGS. 21A-C,there may be no need for time variation in the lamp intensities. Thusthe varying lamp brightnesses shown in FIG. 24 may be sustainedthroughout the entire epitaxial deposition cycle. It may also bedesirable to combine the lamp sequencing methods from FIGS. 21A-C withthe method from FIG. 24.

It will be understood by those skilled in the art that the foregoingdescriptions are for illustrative purposes only. A number ofmodifications to the above epitaxial reactor design and systemconfiguration are possible within the scope of the present invention,such as the following.

The invention is not limited to epitaxial deposition but may be appliedto deposition of polycrystalline or amorphous layers. Although theinvention is particularly useful with monocrystalline siliconsubstrates, the substrates may be composed of other material and havedifferent crystalline structure. Further, the invention may be appliedto other semiconductor structures including electronic integratedcircuits.

The epitaxial reactor may be configured with one, two, or more than twolamp modules illuminating a multi-sided wafer sleeve.

The epitaxial reactor orientation may be changed to embody process gasflow, purge gas flow, and exhaust pumping along a non-vertical axis. Theports for the process gas, purge gas, and exhaust may be on the sameside of the reactor chamber.

Wafers within the wafer sleeve may be attached with good thermal contactto the carrier plates of the wafer sleeve using a number of clampingschemes other than shoulder screws.

Cooling of the lamps within the lamp module may be effected using gasesother than air. For example a non-oxidizing gas might be used to reducethe possibility of oxidative damage to the reflectors within the lampmodule.

Various numbers of lamps within each lamp module are possible other thanthe numbers of lamps shown in the schematic illustrations herein.

A number of water cooling channel configurations within the lamp moduleare possible, other than the serpentine pattern shown herein.

The wafer sleeve may be configured with carrier plates having integralend caps, thereby eliminating the need for separate end caps andreducing parts count.

The illumination window may be fabricated from a clear material otherthan quartz, and with thicknesses differing from a range near 10 mm.

The overall epitaxial reactor system may be configured with a number ofreactor modules different from the quantities illustrated in theembodiments herein. In addition, the epitaxial reactor system may beconfigured without a preheat chamber, or possibly without a cool downchamber, wherein the heat-up and cool-down functions performed by thesemodules in the embodiments shown herein could be performed by chamberswhich are separated from the epitaxial reactor system.

The lamp sequencing procedure may employ more complex illuminationstrategies to linearize the deposition rates in cases where thevariation in deposition rate along the direction of process gas andexhaust flows is more complex than a simple concave curve.

In systems with multiple numbers of reactors, it is possible to employ alamp sequencing procedure in successive reactors wherein the processflows have different directions, instead of using cross-flow processingwithin each reactor.

The orientations of the lamps within lamp modules attached to differentreactor modules may be different.

1. A method for simultaneously depositing semiconductor films bychemical vapor deposition in depletion mode on a multiplicity ofsubstrates in a reactor system, deposition gases being nonlinearlydepleted along a flow path across the substrates, the nonlineardepletion enabling efficient consumption of deposition gases in a singlepass of said deposition gas through said reactor system, said methodcomprising: detachably mounting said multiplicity of substrates on innersurfaces of a pair of wafer carrier plates; assembling said pair ofwafer carrier plates with said multiplicity of substrates detachablymounted thereon into a wafer sleeve, said pair of wafer carrier platesbeing parallel and said inner surfaces being opposed; inserting saidwafer sleeve into a deposition module of said reactor system fordepositing films; radiantly heating said wafer carrier plates fromoutside of said wafer sleeve; flowing a deposition gas through saidwafer sleeve in a first direction, wherein said deposition gas isdepleted nonlinearly in the flow along said first direction and whereinsaid radiantly heating is controlled to provide a non-uniform carrierplate temperature along said first direction to compensate for thenonlinear process gas depletion for linearizing the decreasingdeposition rate on the surfaces of said multiplicity of substrates alongsaid first direction; and after depositing films in said depositionmodule, removing said wafer sleeve from said deposition module andcooling said wafer sleeve in a cool down module; wherein said reactorsystem comprises said deposition module and said cool down module. 2.The method of claim 1, further comprising: before inserting said wafersleeve into said deposition module, preheating said wafer sleeve in apreheating module; wherein said reactor system further comprises saidpreheating module.
 3. The method of claim 1, wherein said radiantlyheating includes irradiating said wafer sleeve from two lamp arrays oflinear incandescent lamps, said lamps being in planes parallel to saidwafer carrier plates and extending linearly in a direction perpendicularto said first direction, the first and second of said lamp arrays beingon opposite sides of said wafer sleeve.
 4. The method of claim 3,wherein incandescent lamps in each of said two lamp arrays are operatedat different power levels.
 5. The method of claim 1, further comprising,after said flowing said deposition gas through said wafer sleeve in saidfirst direction: flowing said deposition gas through said wafer sleevein a second direction, said second direction being opposite to saidfirst direction; wherein said deposition gas is depleted nonlinearly inthe flow along said second direction and wherein, during said flowing insaid second direction, said radiantly heating is controlled to provide anon-uniform carrier plate temperature along said second direction tocompensate for the nonlinear process gas depletion for linearizing thedecreasing deposition rate on the surfaces of said multiplicity ofsubstrates along said second direction.
 6. The method of claim 3,further comprising managing the temperature of said incandescent lampsusing a cooling means.
 7. The method of claim 1, wherein said depositiongas includes a silicon-containing gas and said films are epitaxiallydeposited on said multiplicity of substrates.
 8. The method of claim 7,wherein said deposition gas includes trichlorosilane and hydrogen. 9.The method of claim 7, wherein said multiplicity of substrates aresingle crystal silicon wafers.
 10. The method of claim 7, wherein saidfilms are silicon films.
 11. The method of claim 1, wherein saidassembling includes detachably mounting said pair of wafer carrierplates with said multiplicity of substrates detachably mounted thereonto two end caps to form said wafer sleeve, said two end caps determiningthe spacing between said inner surfaces of said pair of wafer carrierplates, and wherein said two end caps and said pair of wafer carrierplates form a processing cavity, said processing cavity being closed onfirst opposing ends by said end caps and open on second opposing ends.12. The method of claim 11, wherein the ratio of the distance betweensaid end caps and said spacing between the inner surfaces of said wafercarrier plates in said wafer sleeve is at least 20 to
 1. 13. The methodof claim 11, wherein the ratio of the distance between said end caps andsaid spacing between the inner surfaces of said wafer carrier plates insaid wafer sleeve is greater than 40 to
 1. 14. The method of claim 1,wherein said radiantly heating includes active feedback from pyrometersto lamp control electronics for precise dynamic control of thetemperature of said wafer sleeve.
 15. The method of claim 1, whereinsaid radiantly heating includes irradiating said wafer sleeve from alamp array of linear incandescent lamps, said lamps being in a planeparallel to said wafer carrier plates and extending linearly in adirection perpendicular to said first direction.
 16. The method of claim15, wherein incandescent lamps in said lamp array are operated atdifferent power levels.
 17. The method of claim 15, wherein said lamparray includes a reflector for directing radiation to said wafer sleeve.18. The method of claim 15, further comprising cooling said incandescentlamps.
 19. The method of claim 18, wherein said cooling includes flowinga cooling gas along each of said lamps.
 20. The method of claim 18,wherein said cooling includes supplying cooling gas to middle portionsof said lamps, flowing said cooling gas over the length of said lampsand exhausting said cooling gas at exhaust ports disposed near oppositeends of said lamps.
 21. The method of claim 1, further comprisingexposing an exterior of said wafer sleeve to a non-depositing purge gas,wherein a pressure of said purge gas on said exterior is greater than apressure of said deposition gas in the interior of said wafer sleeve.22. The method as in claim 5, wherein said flowing in said firstdirection followed by said flowing in said second direction providefilms of uniform thickness over the surfaces of said multiplicity ofsubstrates.
 23. The method as in claim 1, wherein said first directionis parallel to the surfaces of said multiplicity of substrates mountedon said inner surfaces of said pair of wafer carrier plates.
 24. Themethod as in claim 1, wherein said deposition gas is flowed only in saidfirst direction over the surfaces of said multiplicity of substrates.25. The method as in claim 11, wherein said wafer carrier plates arerectangular plates, and wherein said first direction is parallel to theedges of said wafer carrier plates on said first opposing ends.
 26. Amethod for simultaneously depositing semiconductor films by chemicalvapor deposition in depletion mode on a multiplicity of substrates in areactor system, deposition gases being nonlinearly depleted along a flowpath across the substrates, the nonlinear depletion enabling efficientconsumption of deposition gases in a single pass of said deposition gasthrough said reactor system, said method comprising: detachably mountingsaid multiplicity of substrates on inner surfaces of a pair of wafercarrier plates; assembling said pair of wafer carrier plates with saidmultiplicity of substrates detachably mounted thereon into a wafersleeve, said pair of wafer carrier plates being parallel and said innersurfaces being opposed; inserting said wafer sleeve into a depositionmodule of said reactor system for depositing films; radiantly heatingsaid wafer carrier plates from outside of said wafer sleeve; flowing adeposition gas through said wafer sleeve in a first direction, whereinsaid first direction is parallel to the surfaces of said multiplicity ofsubstrates mounted on said inner surfaces of said pair of wafer carrierplates, wherein said deposition gas is depleted nonlinearly in the flowalong said first direction, wherein said radiantly heating includesirradiating said wafer sleeve from two lamp arrays of linearincandescent lamps, said lamps being in planes parallel to said wafercarrier plates and extending linearly in a direction perpendicular tosaid first direction, the first and second of said lamp arrays being inequivalent positions on opposite sides of said wafer sleeve, and whereinsaid radiantly heating is controlled to vary the radiant intensity atsaid wafer carrier plates along said first direction; and afterdepositing films in said deposition module, removing said wafer sleevefrom said deposition module and cooling said wafer sleeve in a cool downmodule; wherein said reactor system comprises said deposition module andsaid cool down module.
 27. The method as in claim 26, wherein said lampsin each of said two lamp arrays are organized into portions as measuredalong said first direction, said portions comprising first portions atthe beginning of said two lamp arrays, second portions in the centers ofsaid two lamp arrays and third portions at the ends of said two lamparrays, wherein the illumination levels of said first, second and thirdportions are independently controllable, and wherein the illuminationlevels of said first, second and third portions in the first of said twolamp arrays are the same as the illumination levels of said first,second and third portions, respectively, in the second of said two lamparrays.
 28. The method as in claim 27, wherein said radiantly heatingincludes operating said first portions of said two lamp arrays at adifferent illumination level from said second portions of said two lamparrays.
 29. The method as in claim 27, wherein said radiantly heatingincludes operating said second portions of said two lamp arrays at adifferent illumination level from said third portions of said two lamparrays.
 30. The method of claim 26, further comprising: before insertingsaid wafer sleeve into said deposition module, preheating said wafersleeve in a preheating module; wherein said reactor system furthercomprises said preheating module.
 31. The method of claim 26, furthercomprising, after said flowing said deposition gas through said wafersleeve in said first direction: flowing said deposition gas through saidwafer sleeve in a second direction, said second direction being oppositeto said first direction; wherein said deposition gas is depletednonlinearly in the flow along said second direction, and wherein, duringsaid flowing in said second direction, said radiantly heating iscontrolled to vary the radiant intensity at said wafer carrier platesalong said second direction.
 32. The method as in claim 31, wherein saidflowing in said first direction followed by said flowing in said seconddirection provide films of uniform thickness over the surfaces of saidmultiplicity of substrates.
 33. The method of claim 26, furthercomprising managing the temperature of said incandescent lamps using acooling means.
 34. The method of claim 26, wherein said deposition gasincludes a silicon-containing gas and said films are epitaxiallydeposited on said multiplicity of substrates.
 35. The method of claim34, wherein said deposition gas includes trichlorosilane and hydrogen.36. The method of claim 34, wherein said multiplicity of substrates aresingle crystal silicon wafers.
 37. The method of claim 34, wherein saidfilms are silicon films.
 38. The method of claim 26, wherein saidassembling includes detachably mounting said pair of wafer carrierplates with said multiplicity of substrates detachably mounted thereonto two end caps to form said wafer sleeve, said two end caps determiningthe spacing between said inner surfaces of said pair of wafer carrierplates, and wherein said two end caps and said pair of wafer carrierplates form a processing cavity, said processing cavity being closed onfirst opposing ends by said end caps and open on second opposing ends.39. The method of claim 38, wherein the ratio of the distance betweensaid end caps and said spacing between the inner surfaces of said wafercarrier plates in said wafer sleeve is at least 20 to
 1. 40. The methodof claim 38, wherein the ratio of the distance between said end caps andsaid spacing between the inner surfaces of said wafer carrier plates insaid wafer sleeve is greater than 40 to
 1. 41. The method as in claim38, wherein said wafer carrier plates are rectangular plates, andwherein said first direction is parallel to the edges of said wafercarrier plates on said first opposing ends.
 42. The method of claim 26,wherein said radiantly heating includes active feedback from pyrometersto lamp control electronics for precise dynamic control of thetemperature of said wafer sleeve.
 43. The method of claim 26, whereinsaid lamp array includes a reflector for directing radiation to saidwafer sleeve.
 44. The method of claim 26, further comprising coolingsaid incandescent lamps.
 45. The method of claim 44, wherein saidcooling includes flowing a cooling gas along each of said lamps.
 46. Themethod of claim 44, wherein said cooling includes supplying cooling gasto middle portions of said lamps, flowing said cooling gas over thelength of said lamps and exhausting said cooling gas at exhaust portsdisposed near opposite ends of said lamps.
 47. The method of claim 26,further comprising exposing an exterior of said wafer sleeve to anon-depositing purge gas, wherein a pressure of said purge gas on saidexterior is greater than a pressure of said deposition gas in theinterior of said wafer sleeve.
 48. The method as in claim 26, whereinsaid deposition gas is flowed only in said first direction over thesurfaces of said multiplicity of substrates.